1. Field of the Invention
The present invention pertains generally to various cutting tools such as die rule blades, slitter blades, and the like, commonly used in production line presses for cutting a stock material in bulk and more particularly to a novel cutting edge configuration using a chisel-like tooth. See Disclosure Document 054,341.
2. Description of the Prior Art
The art to which this invention pertains has been well developed in recent years. As more production lines are automated and new materials are introduced, the need for an improved cutting rule which would achieve cutting with reduced applied force, prolong the life of die cutting equipment, reduce the need for frequent cutting rule replacements and which yields cleaner cuts of the stock material has stimulated many new designs and much experimentation with cutting rule on various types of stock materials. Patents in this art include U.S. Pat. No. 3,203,295 and more recently U.S. Pat. Nos. 3,855,892; 3,961,858 and 4,002,092. The prior art in cutting rule and the problems encountered in the present art are discussed in these patents. These patents indicate trends in cutting rule design, which the present novel design continues only in part. The present invention is directed in particular to yielding a cleaner cut than possible with the die cutting rule of these patents.
U.S. Pat. No. 3,855,892 discloses a cutting blade having an asymmetric sawtooth cutting edge in which the depth of the notch is less than half the distance between the adjacent teeth tips, said teeth tips being sharply pointed. U.S. Pat. No. 3,961,858 discloses a compound angle cutting edge configuration having piercing points and slicing edges extending away from one peak downward into an adjacent notch and up to the next peak at a different angle, thus resulting in an assymmetrical configuration having shallow notches. U.S. Pat. No. 4,002,092 also shows the cutting edge of U.S. Pat. No. 3,961,858. In these patents there are three common features, an asymmetric tooth design, a sharp piercing point on the tooth and shallow notches or crotches between the teeth.
The use of a sharp, piercing tooth tends to rip the stock material at the point of penetration. The asymmetric tooth design results in a leaning tooth which, in the embodiment of U.S. Pat. No. 4,002,092, has notches which are too shallow and hence requires more press force to penetrate the stock material. In general, the trend toward shallow teeth is effective when the depth of the crotch is integrated with the tooth design because the blade does not cut until the teeth have fully penetrated the stock material.
U.S. Pat. No. 3,203,295, cited in the prosecution of the parent application teaches a rule having curved apices and valleys and not the sharp spaces or valleys as proposed herein. The radius in the valley of the tooth disclosed therein causes a less smooth cut, increased pressure to cut and an imbedding of the cut material (trapped in the rounded valleys) into the blanket material reducing the latter's life. Further, it teaches the use of slots formed in the body portion to facilitate forming of the rule, whereas the slot of the present invention has been formed to greatly facilitate the curving of the rule as best seen in FIG. 10.
After extensive experimentation with teeth designs and cutting edges, including those disclosed in the above-cited patents, the design of the present invention has evolved to solve the problems still remaining in die cutting many stock materials.